This is a competing renewal application for a postdoctoral T32 training grant in laboratory-based transplantation biology. Solid organ transplantation is the ideal therapy for end stage failure due to kidney, heart, liver, and lung, disease, among other organs. Despite significant improvements in the care of all solid organ transplant recipients long term allograft survival remains suboptimal. Analogously, bone marrow transplantation is an effective therapy for hematologic malignancies, but acute (and chronic) graft versus host disease occurs commonly and causes significant morbidity. Moreover, while scientific progress has increased knowledge, the causes of graft loss (and GVHD) are only partially understood, reliable tolerance induction protocols remain elusive, and the ability to translate what information is available into useful diagnostic, preventive and treatment modalities in patients has been limited. To continue to improve transplant outcomes in humans and as a consequence, improve the long term health of all transplant recipients, research in transplantation must remain cutting edge, and the next generation of physicians/scientists must have the appropriate knowledge base and skills to continue to drive the field forward. Because transplantation is a cross disciplinary field involving multiple medical, surgical, and basic pathology/immunology themes, we believe an effective training environment must be cross-disciplinary. Thus, the objective of this training program is to use an interactive, collaborative, cross-disciplinary approach to train talented young physician-scientists (MD and MD PhD) or PhD-scientists for a successful career in laboratory based, investigative, transplantation immunobiology research. In support of the renewal application, the initial funding period of this training program has been successful in accomplishing the key aim of fostering the careers of trainees in transplantation, in particular, underrepresented minorities. Our rationales for submitting this competitive renewal grant application include: 1) the continued need for improving outcomes following solid organ or hematopoietic cell transplantation, 2) our strong desire to continue to have an impact on the education of future investigators in the field of transplantation, and 3) our belief that the proposed group of trainers will offer diverse basic and translational scientific opportunities within the field of transplantation supported by an established infrastructure designed for training and nurturing young transplant researchers toward independence. We have a diverse and well funded faculty with an interest in transplantation and a strong pool of trainees that includes significant numbers of underrepresented minorities. The program is overseen by P Heeger, who is well recognized and accomplished clinical and basic physician scientist with significant postdoctoral training, and educational, experience. The program is designed to support laboratory based training by individual mentors performing research in transplantation medicine/biology. The cross disciplinary program is supplemented with significant didactic training in transplantation science, grant writing, manuscript preparation and career development so as to optimize the development of independent academic researchers in the transplant field.